Hey guys,
Here's what I have found out trying this. If a new lead is filling out the form, the lead needs to be created before parameters like "email address", etc, can be passed through to the follow up page. I'm no coder, but the way I've figured this out is to direct first to a Marketo follow up page for, say, 3 seconds (and have that page say, like, "please wait"), and then redirect to the url with all those token parameters -- this allows for the time it takes for the lead to be created in Marketo and then be able to be gathered and submitted. I was working with a client on this and we tried it and it worked. Don't know if this is what you were trying to do, but if so, give it a shot!
Jono